Xeljanz Side Effects May Cause Weight Gain: Study

Researchers say weight gain is just one of many serious side effects linked to Xeljanz, which has also been associated with increased risks of cancer and blood clots.

A new study suggests that Xeljanz may cause significant weight gain as a side effect, potentially increasing the risk of additional health complications such as heart disease and metabolic problems like high cholesterol.

The findings were published in the journal ACR Open Rheumatology on May 9, by an international group of researchers, funded through Xeljanz’s manufacturer, Pfizer, indicating that Xeljanz users face the potential for a 5% weight increase in just the first three months of use. 

Xeljanz (tofacitinib) was introduced by Pfizer in 2012, joining the lucrative market for treatments of individuals with rheumatoid arthritis (RA), psoriatic arthritis and ulcerative colitis. It was the first of a class of medications known as Janus Kinase (JAK) inhibitors.

JAK inhibitors, which block the JAK enzymes in the body, are used to treat a wide variety of conditions ranging from autoimmune diseases like Crohn’s disease, rheumatoid arthritis and alopecia, as well as COVID-19 and other inflammatory ailments. They are also commonly used to treat dermatological conditions, such as eczema and atopic dermatitis.

In the new study, a team of researchers led by Jürgen Wollenhaupt conducted an analysis of several clinical trials involving Xeljanz use. The data included 5,335 patients who used the medication, including 2,349 who took 5 mg of Xeljanz twice daily, 1,611 who took 10 mg twice daily, 694 who took 11 mg once daily, and 681 patients who were given a placebo.

Regardless of the size or frequency of dose, the researchers determined that all Xeljanz users faced an increased risk of weight gain and increased body mass index (BMI) when compared to those taking a placebo.

Wollenhaupt’s team determined that a “significantly greater” proportion of Xeljanz users saw 5% or more increases in weight at three months and six months. Those increases lasted through at least the first year, the data indicates.

The data also revealed a correlation between Xeljanz use weight changes and lipid levels, although the correlation was weak. However, the researchers called for more studies into the long-term effects.

“Weight and BMI continued to increase through 12 months of observation in the studies, so a new equilibrium had not yet been reached,” the researchers reported. “Longer term observations are warranted to establish whether there is sustained weight gain, if this varies by tofacitinib dose, and if there are any health implications of continued weight gain.”

Xeljanz Health Concerns

The findings add to concerns that have emerged in recent years over other side effects of Xeljanz, and similar JAK inhibitors, which have been linked to blood clots and cancer risks in recent years.

Concerns over potential Xeljanz cancer risks and other side effects began to emerge in early 2021, after preliminary data from a post-marketing study linked Xeljanz to an increased risk of cancer, heart attacks, strokes and deadly blood clots.

These findings have resulted in a number of Xeljanz lawsuits being filed by former users diagnosed with cancer, pulmonary embolism and other injuries, alleging that drug makers failed to adequately research the side effects of JAK inhibitors and warn about potential risks compared to older TNF inhibitors.

Although each of the complaints raises similar questions of fact and law, there are not currently any consolidated pretrial proceedings in the federal court system, and each of the lawsuits is moving forward as individual claims.